Crank with adjustable crank radius

ABSTRACT

In adjustable throw cranks, it is desirable to take up any play in the mechanical adjusting mechanism. The play is taken up using a pressure fluid thrusting device which thrusts the crank pin towards the axis of rotation of the crankshaft. This is particularly useful in flying shears where the force of the shear blade is opposed to centrifugal force.

United States Patent Fritz I CRANK WITH ADJUSTABLE CRANK RADIUS Inventor:

Assignee:

dorf, Germany June 29, 1970 Filed: Aopl. No.:

Manfred Fritz, Erkrath, Germany Schloemann Aktiengesellschaft, Dussel- Foreign Application Priority Data 1451 June 27, 1972 [56] References Cited UNITED STATES PATENTS 1,910,387 5/1933 Hahn ..83/344 X 3,436,988 4/1969 Simonton 74/600 X Primary Examiner-James M. Meister Attorney-Holman & Stern 57 ABSTRACT in adjustable throw cranks, it is desirable to take up any play in the mechanical adjusting mechanism. The play is taken up using a pressure fluid thrusting device which thrusts the crank pin towards the axis of rotation of the crankshaft. This is particularly useful in flying shears where the force of the shear blade is opposed to centrifugal force.

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PATENTEnJunm 1972 SHEET 2 OF 4 Fig. 2

IN VEN TOR MANFREI] FRIIZ BY 1 1 LLMQRJYQ) A rn bu rs PATENTEDJUH 21 m2 3, 572 242 saw u or 4 INVENTOR MANFREU FRIIZ CRANK WITH ADJUSTABLE CRANK RADIUS The invention relates to an adjustable throw crank having a crank pin which can be moved radially and mechanical means for adjusting the radial position of the crank pin. Such mechanical means may comprise an internally screw-threaded bore in a crank arm, an externally screw-threaded spindle rotatably mounted in a non-adjustable part of the crank, and means for rotating the spindle to change the radial position of the crank arm.

Such adjustable throw cranks are used for example in rotating shears (also called flying shears) in order to change the peripheral speed of the cutting blade whilst keeping the same speed of revolution. In this way it is possible to alter the cut lengths of the material being cut by altering the delivery speed of the material and altering the distance of the crank axis of rotation from the material to correspond with the alteration of radius of the cutting blade. One should note, however, that the centrifugal force acting on the crank is in the opposite direction to the cutting force at the moment of shearing. In order to avoid the spindle jumping the length of the spindle play inside the internally screw-threaded bore at this moment, i.e. the spindle jumping until the previously unloaded faces of the screw-thread abut one another, the loaded faces of the screw thread are suitably pressed against each other by means of a thrusting device. In one construction, the thrusting device consists of a lock-nut which bears against the internally screwthreaded bore.

This thrusting device has however a number of disadvantages. The use of this thrusting device is very troublesome because the lock-nut must be loosened by hand every time the crank throw is altered and must be again tightened up after the alteration. In addition, for constructional reasons, the lock-nut can only be screwed onto the end of the spindle which projects out of the internally screw-threaded bore, so that the crank pin is thrust in the same direction as that in which the centrifugal force operates. However, the cutting force which occurs at the moment of shearing is considerably larger than this centrifugal force. If one wants to avoid the jump or play in the screw thread, the lock-nut must be so strongly tightened that the tightening force is larger than the cutting force. This causes great wear of the screw thread.

It is a general object of the invention to provide a crank in which the mechanical adjusting means can be quickly and easily actuated and in which there is sufficient thrusting force to prevent play in the adjusting means.

According to the present invention, there is provided an adjustable throw crank having:

a crank pin which can be moved radially,

mechanical'means for adjusting the radial position of the crank pin, and

a pressure fluid (preferably hydraulic) operated thrusting device for taking up any play in the mechanical adjusting means by thrusting the crank pin towards the axis of rotation of the crank shaft, the thrusting device normally having at least one pressure fluid ram connecting the crank pin to a nonadjustable part of the crank.

required to adjust the mechanical adjusting means, e.g., to turn the screw-threaded spindle.

In order to keep this adjustment force small even with large crank radii, and thereby to reduce wear on the mechanical ad- 5 justing'means (e.g., on the screw threads), the thrusting device may be actuated by centrifugal force created when the crank rotates; if the thrusting device has at least one pressure fluid thrusting ram connecting the crank pin to a non-adjustable part of the crank, for thrusting the crank pin, there may be a further ram connected to said thrusting ram(s), a radially movable centrifugal body and means mechanically connecting the centrifugal body to said further ram such that rotation of the crank causes the centrifugal body to pressurize the pressure fluid in said further ram and hence pressurize the pressure fluid in said thrusting ram(s); i.e., the further ram is so positioned on the crank and so cooperates with the centrifugal body that the piston of the further ram is thrust into the cylinder when the crank rotates. If there is a pressure fluid reservoir connected to the thrusting device, a check valve can be provided between said thrusting ram(s) and the reservoir to prevent pressure fluid flowing into the reservoir when the crank rotates.

This construction has the advantage that as the crank rotates, the centrifugal body presses the pressure fluid out of said further ram into said thrusting ram(s) and hence increases the thrusting pressure in the same way as the centrifugal force acts on the crank pin. In this manner, the pressure in the reservoir can be kept relatively small so that the mechanical adjusting means can be adjusted with ease when the crank is stationary.

The thrusting device may be pressurized by a fixed pressure I fluid pump or by a fixed pressure reservoir. For this purpose, it is necessary to have a rotating coupling in the pressure lead from the pump or reservoir to the thrusting device, at a certain position on the crank. This rotating coupling complicates the construction of the thrusting device and causes an additional leakage loss.

In order to avoid this leakage loss and to simplify the construction of the crank, a pressure fluid reservoir may be fixed to the crank (preferably to a non-adjustable part of the crank) and connected to the thrusting device.

The air pressure in the pressure reservoir must be sufficient at every possible radius of the crank pin to exceed the centrifugal force acting on the crank pin and to bring the bearing faces of the mechanical adjusting means (e.g., of the screw threads) into contact in a direction opposed to that of the centrifugal force. If the crank radius is large, a correspondingly larger force is required so that a large adjustment force is Thus in general, in a crank in accordance with the invention, the thrusting device can be arranged such that friction between the bearing surfaces (e.g., between the bearing surfaces of the screw threads) is reduced and wear between these bearing surfaces is lessened. In addition, the thrusting device can be arranged to. be self-contained and require no parts which do not rotate with the crank.

The crank of the invention can be used in any suitable machine, particularly in machines where one experiences the problems that one has with flying shears. This invention extends to a flying shear having the crank of the invention for driving the shear blade, the blade being mounted on the crank pm.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a view of the crank, looking in the direction of the crank pin;

FIG. 2 is a section through the crank along the line IIIl of FIG. 1;

FIG. 3 is a section through the crank along the line III-III of FIG. 2; and

FIG. 4 is a schammatic diagram of the thrusting device with the pressure leads between the rams and the pressure reservorr.

The crank shown in FIG. 1 has a crankshaft flange l which rotates about an axis M A crank arm 2 having a radially movable crank pin 3, is fixed to the crankshaft flange 1. The axis M of the crank pin 3 rotates about the axis M at a radius R. This radius can be altered according to the required speed of the crank pin 3.

The internal construction of the crank can be seen in FIGS. 2 and 3. The crankshaft flange 1 is a part of a shaft 4 which is carried in a housing 5 by means of a bearing 6. A toothed pinion 7 is fixed to the crankshaft 4, the toothed pinion being driven in a conventional manner by a motor (not shown).

An internally screw-threaded bush 9 is fixed to the crank arm 2, the bush 9 cooperating with a screw-threaded part 10 on a screw-threaded spindle 8 which is rotatably mounted in the crankshaft flange 1. A collar 11 is provided for fixing the spindle 8 against movement radial to the crankshaft axis, the collar 11 hearing against a bearing bush 13 by way of a bevel gear 12; the spindle 8 is rotatably mounted in the bearing bush 13. The bearing bush 13 sits in a lug l4 projecting from the crankshaft flange l. The spindle 8 is also fixed against movement in a radial direction by means of a ring nut bearing against the lug 14 by way of an intermediate ring 16, an axial bearing 17 and a distance bush 18. The spindle 8 is rotated by means of a shaft 20, a bevel gear 19 and the bevel gear 12; the shaft 20 is supported by a bearing 21 in a central bore in the crankshaft 4, and can be driven in the normal manner by a separate drive which is not shown. The crank arm 2 is slidably guided in the radial direction-at three positions, by means of the sliding bushes 22 and 23.

The cooperating faces of the screw threads of the spindle 8 and the bush 9 are pressed against each other by means of a thrusting device which is described in detail below. The cylinders 24 of two hydraulic rams are connected to the crankshaft flange l at each side of the crank arm 2 by means of stirrups or pipe clamps 26.

The cylinders 24 have piston rods 25 which have collars 27 bearing against lateral projections 28 on the crank arm 2, and the piston rods have their extended end portions guided in the sliding bushes 23. The cylinder spaces in the cylinders 24 are connected with a pressure reservoir 29 by means of pressure leads 30 and 31, the pressure reservoir 29 being fixed to the crankshaft flange l.

The cylinder spaces of the rams 24, 25 are connected with the cylinder space of a further ram 33, 34 whose cylinder 33 is pivoted to the crankshaft flange 1 by means of a laterally projecting pivot pin 35. The piston rod 34 of the cylinder 33 is connected by means of a pin 36 with a body 37 which can slide radially to the axis M the body 37 is pivoted about a pin 38 fixed to the crankshaft flange l in such a way that when the crank is rotating, the piston rod 34 is thrust into the cylinder 33 under the influence of centrifugal force acting on the body 37. In this way, the liquid in the cylinder 33 is forced into the cylinder spaces of the rams 24, 25 and the thrusting force acting on the crank arm 2 is correspondingly increased. However, as can be seen in FIG. 4, a check valve 32 is required between the cylinder spaces of the rams 24, 25 and the pressure reservoir 29 in order to prevent flow back into the pressure reservoir lest the air cushion in the pressure reservoir 29 considerably reduces the extra pressure that has been obtained.

As shown in FIG. 4 a further opening 40 is provided in the centrifugally actuated ram 33, 34, which opening is directly connected with the pressure reservoir 29 by way of a pressure lead 41. This opening is only open for liquid flow when the piston rod 34 is in its extended position. The opening 40 is blocked as soon as the piston rod 34 is pushed a little into the cylinder 33 when the crankshaft begins to rotate.

The advantage of the opening 40 is that the-pressure fluid can flow out of the cylinder spaces of the rams 24, 25, through the ram 33, 34 and into the pressure reservoir 29 when the crank is still, if the crank radius R is to be increased. if this were not so, it would be necessary to insert an on/off valve in parallel to the check valve 32. The centrifugal body 37 has also a nose 44 which, when the crank is still (as shown), lies against an abutment 42 on the crankshaft flange l. A further abutment 43 for the nose 44 limits the stroke of the piston rod I claim:

1. An adjustable throw crank having a non-adjustable part,

a crank pin which can be moved with respect to the non-adjustable part in a direction which is radial to the axis of rotation of the crank,

mechanical means for adjusting the radial position of the crank pin, and

a pressure fluid operated thrusting device for taking up any play in the mechanical adjusting means by thrusting the crank pin towards the axis of rotation of the crank.

2. A crank as claimed in claim 1, and including a pressure fluid reservoir fixed to the crank and connected to the thrusting device.

3. A crank as claimed in claim 1, wherein the thrusting device comprises means rotating with the crank and sensitive to centrifugal force to thrust the crank pin towards the axis of rotation of the crank.

4. A crank as claimed in claim 3, wherein the thrusting device has at least one pressure fluid thrusting ram connecting the crank pin to the non-adjustable part of the crank, for thrusting the crank pin towards the axis of rotation of the crank, a further ram connected to said thrusting ram, a radially movable centrifugal body, and means mechanically connecting the centrifugal body to said further ram whereby rotation of the crank causes the centrifugal body to increase the pressure of the pressure fluid in said further ram and hence in said thrusting ram. 5. A crank as claimed in claim 4, and including a pressure fluid reservoir fixed to the crank and connected to said thrusting ram, and a check valve between said thrusting ram and the reservoir to prevent pressure fluid flowing into the reservoir when the crank rotates.

6. A crank as claimed in claim 5, and having a further connection connecting said further ram to the pressure fluid reservoir, said further connection being shut when the crank is not rotating.

7. A crank as claimed in claim 6, wherein said further ram has a cylinder, a piston, and a piston rod, said cylinder having a side wall defining an opening to provide said further connection, the opening leading into the pressure space of the ram when the piston rod is extended, but being closed from the pressure space of the ram when the piston rod is thrust in by the centrifugal body.

8. A crank as claimed in claim 1, wherein the mechanical adjusting means has a crank arm guided for radial movement,

an internally screw-threaded bore in the crank arm,

an externally screw-threaded spindle rotatably mounted in the non-adjustable part of the crank, and

means for rotating the spindle to change the radial position of the crank arm. 

1. An adjustable throw crank having a non-adjustable part, a crank pin which can be moved with respect to the nonadjustable part in a direction which is radial to the axis of rotation of the crank, mechanical means for adjusting the radial position of the crank pin, and a pressure fluid operated thrusting device for taking up any play in the mechanical adjusting means by thrusting the crank pin towards the axis of rotation of the crank.
 2. A crank as claimed in claim 1, and including a pressure fluid reservoir fixed to the crank and connected to the thrusting device.
 3. A crank as claimed in claim 1, wherein the thrusting device comprises means rotating with the crank and sensitive to centrifugal force to thrust the crank pin towards the axis of rotation of the crank.
 4. A crank as claimed in claim 3, wherein the thrusting device has at least one pressure fluid thrusting ram connecting the crank pin to the non-adjustable part of the crank, for thrusting the crank pin towards the axis of rotation of the crank, a further ram connected to said thrusting ram, a radially movable centrifugal body, and means mechanically connecting the centrifugal body to said further ram whereby rotation of the crank causes the centrifugal body to increase the pressure of the pressure fluid in said further ram and hence in said thrusting ram.
 5. A crank as claimed in claim 4, and including a pressure fluid reservoir fixed to the crank and connected to said thrusting ram, and a check valve between said thrusting ram and the reservoir to prevent pressure fluid flowing into the reservoir when the crank rotates.
 6. A crank as claimed in claim 5, and having a further connection connecting said further ram to the pressure fluid reservoir, said further connection being shut when the crank is not rotating.
 7. A crank as claimed in claim 6, wherein said further ram has a cylinder, a piston, and a piston rod, said cylinder having a side wall defining an opening to provide said further connection, the opening leading into the pressure space of the ram when the piston rod is extended, but being closed from the pressure space of the ram when the piston rod is thrust in by the centrifugal body.
 8. A crank as claimed in claim 1, wherein the mechanical adjusting means has a crank arm guided for radial movement, an internally screw-threaded bore in the crank arm, an externally screw-threaded spindle rotatably mounted in the non-adjustable part of the crank, and means for rotating the spindle to change the radial position of the crank arm. 